We have two Windows Server 2003 DCs running DNS that have been allowing name resolution of internet sites just fine for a few weeks. I'll call them "DNS-1" and "DNS-2" for reference. DNS-1 is the primary DNS server and the first DC we brought online. Suddenly, yesterday the DNS servers quit resolving names of internet sites.
If it helps we are currently running both this 2003 test AD domain and a production NT 4 domain (each domain trusts the other). There are separate DNS servers on each domain. As stated, a couple weeks ago when we set this up all name resolutions worked fine from either domain when using the DNS. The same name records exist on the DNS servers in both domains.
There are not any blatant DNS errors in the Event logs for DNS or AD. You can ping outside IP addresses just fine from either AD DNS servers, but it will not resolve names. I've run NETDIAG and DCDIAG, and AD and DNS both come back with "pass" on the tests.
I can't point to any recent changes in our network, so that doesn't seem to be the case, but because I see no errors on DNS-1 or DNS-2.
I've verified the DNS settings on the servers per Microsofts "best practices for DNS", and this thing worked great with no real explanation as to the sudden problems.....
I'm no DNS expert, so any advice on additional troubleshooting tools, etc.